Radioactive waste materials are generated at a number of different sources, including nuclear power plants, nuclear weapons facilities, and nuclear fuel processing facilities. There are also a number of less obvious sources of radioactive wastes. For example, the fly ash of coal power plants may include radioactive constituents. Also, radioactive materials are used in certain medical procedures. Thus, medical facilities are major producers of radioactive waste materials. The radioactive wastes produced at medical facilities include equipment and clothing which may be contaminated by the radioactive material used in medical procedures.
The three types of radiation emitted from radioactive materials are alpha, beta, and gamma radiation. Alpha and beta radiation comprise particles which are emitted from the nucleus of an atom, while gamma radiation comprises short-wavelength photons of nuclear origin. Alpha particles are doubly ionized helium nuclei, and thus have a net positive electrical charge. Beta radiation comprises primarily electrons, although some radioactive isotopes emit positrons which are also referred to as beta particles. Both the charged alpha particles and beta particles may be deflected by an electromagnetic field, although beta particles are deflected more easily due to their lower mass. Gamma radiation is either emitted from a radioactive material directly or emitted as the result of a collision between an alpha or beta radiation particle and some other particle.
Radioactive materials may emit one or more of the three different types of radiation, alpha, beta, of gamma radiation. Many radioactive materials emit primarily only alpha particles and/or beta particles, but produce gamma radiation indirectly as the high-energy alpha and beta particles collide with other particles.
Wastes which include radioactive materials may be treated in a molten metal process to remove organic materials and to tie up the radioactive material. U.S. patent application Ser. No. 09/096,617, filed Jun. 12, 1998 by the present inventor, discloses an apparatus and method for treating waste streams which include radioactive constituents. The apparatus and method disclosed in Application Ser. No. 09/096,617, which is incorporated herein by reference, removes organic constituents from the mixed waste stream and contains the radioactive constituents. Organic materials in the waste stream react with the molten reactant metal to produce primarily elemental carbon, hydrogen, nitrogen, and metal salts. Radioactive materials in the waste stream are alloyed in the molten metal for eventual storage. The molten metal process disclosed in Application Ser. No. 09/096,617, utilizes radiation absorbing metals such as lead and tungsten, for example, in the molten reactant metal in order to safely absorb radioactive emissions from the alloyed radioactive materials.